pub fn validate_subscribe_accept_header(
headers: &HeaderMap,
) -> Result<(), CratestackError>Expand description
GET /rpc/subscribe/{op_id} has no upgrade handshake to negotiate a
binary subprotocol like WS does — the client states its intent via a
plain Accept header, same as every other HTTP RPC binding. Reject
anything that doesn’t ask for SSE up front, before any
CratestackEventBus subscription gets registered.